SDL_ExitProcess(), SDL_AbortAssertion() and SDLTest_BailOut().
(Commit 303c1e0fb0cf for bug #4100 removed SDL_NORETURN from
SDL_ExitProcess() and SDL_AbortAssertion() in order to avoid
warnings from windows builds, but that's temporary I guess..)
The change makes sure that SDL_vsnprintf() nul terminates if it is
using _vsnprintf() for the job.
I made this patch for Watcom, whose _vsnprintf() doesn't guarantee
nul termination. The preprocessor check can be extended to windows
in general too, if required.
Closes bug #3769.